Chapter 3: Basic Science

Anthropologists have studied the racial and geographical variations in human anatomy very extensively. Unfortunately, neurosurgeons have not paid much attention to the racial or ethnic differences in neuroanatomy

The Skull
Racial differences have been documented in the thickness of the skull. An autopsy study of Black and White adults skulls in Harare, Zimbabwe, revealed that White women had the thickest skull followed by Black women, then Black men and White men. (Ross, Lee & Castle 1976). Adeloye, Kattan and Silverman (1975) in Cincinnati, USA, based on skull radiographic studies found that Black and White females had thicker skulls than males especially in the parietal and occipital bones. They further found that White males had thicker frontal bones than Black males while the reverse was the case for parietal and occipital bones. Ishida and Dodo (1990) in Japan found that the cranial thickness at the frontal and parietal eminence was significantly greater in females than in males. Smith et al (1985) in their study of cranial thickness in Near Eastern populations of Jordan and Israel found no significant differences in cranial thickness between the sexes. Gothlin and Gadeholt (1988) found that the Australian Aborigine had a thicker calvarian bone and a lower forehead profile than modern Scandinavian skulls.
Saxena, Jain and Chowdhary (1988) performed a comparative study of the pterion in the skulls of Nigerians and Indians and found some significant differences. Sphenoparietal pterion was present in 95.3% of Indians and 84.8% of Nigerians. Frontotemporal pterion was seen in 3.46% of Indians and 10.1% of Nigerians. Stellate pterion was found in 1.38% of Indians and 5% of Nigerians. More Nigerians tended to have high pterion, so that its distance from the zygomatic arch was greater. The pterion is an important landmark to the neurosurgeon and its anatomy deserves further investigations in other geographical areas.
Zivanovic (1967) in a study of skulls from East Africa found that elongated styloid process was common in Africans, 30% having processes longer than 25mm and 14% longer than 30mm. In Europeans, only 4% have styloid processes longer than 25mm. De Francisco et al (1990) studied the variations in the hypoglossal canal of 492 human dried skulls from different races. They found no significant racial differences in the anatomy of the hypoglossal canal.

Pineal gland
Racial differences have been noted in the rate of pineal calcification as seen in plain skull radiographs. In Caucasians, calcified pineal is visualised in about 50% of adult skull radiographs after the age of 40 years (Wurtman et al, 1964). Murphy (1968) reported a radiological pineal calcification rate of 2% from Uganda, while Daramola and Olowu (1972) in Lagos, Nigeria had a rate of 5%. Adeloye and Felson (1974) found that calcified pineal was twice as common in White Americans as in Blacks in the same city, thus strengthening the suspicion that there may be a true racial difference. In India a frequency of 13.6% was found (Pande et al, 1984). Calcified pineal gland is a common finding in plain skull radiographs and its value in identifying the midline is still complementary to modern neuroradiological imaging that has diminished this role. Adeloye and Felson (1974) also found that radiological calcification of the falx cerebri was present in 16% of Black Americans but only 3% of Whites.

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